Introduction
The mobile age is as well a challenge for commercial websites to provide e.g. an e-shop running compatible on different mobile devices. See also: Wikipedia: M-commerce!
Retailers are faced with a wide range of various hardware & software conditions. First of all, they have to decide between web or native applications. All these app types keep different advantages & disadvantages. A native shopping app is on the one hand more expansive to build up than a web shopping app. On the other hand a native app allows to use more features of a given device in comparison to a web app. A web app is platform indepentent but mostly doesn't ensure such a high user expierence like a native app.
Web Apps
A web app is mostly created with HTML5, CSS3 & Java Script. And it's executed trough a mobile browser. See also: Wikipedia: Web app & Jonathan Stark, O'Reilly: Building iPhone Apps with HTML, CSS, and JavaScript! Online retailers have to managage a huge amount of data (product catalogues, customers's information, supplier specificatons etc.) via their shop software & they have to assure the security of all electronically safed data.